1 Download Nagios tar using:
=> wget http://prdownloads.sourceforge.net/sourceforge/nagios/nagios-3.2.0.tar.gz
2 Untar it anywhere
=> tar zxf nagios-3.2.0.tar.gz
3 Get into the directory
=> cd nagios-3.2.0
4 configure the nagios using this command
=> ./configure --with-command-group=Nadmin
5 Run Make commands to build up the files to install Nagios
=> make all
6 Then use make install to install the init scripts in directory /etc/rc.d/init.d
=> make install
7 Lets configure permission for holding external files
=> make install-init
8 Install sample config files which can be found later in /usr/local/Nagios/etc
=> make install-config
9 This for commandmode installation
=> make install-commandmode
10 Set your Email Id using:
=> vi /usr/local/Nagios/etc/objects/contacts.cfg

To make the nagios utility to work automatically use this:
=> /sbin/chkconfig --add nagios
Turn the Nagios on :)
=> /sbin/chkconfig nagios on
We need a check config file that can work for for auto start of nagios. To do that use
=> /usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg
done??
Now start the service
/sbin/service nagios start

So here we are done with the nagios installation and configuration ….

For the web interface :
type the following in the URL

http://localhost/nagios orr http://ip/nagios

I tried to write this tutorial as simple as a 2nd standard guy can configure it 🙂 just a joke